The Museum of HP Calculators

Simple adding machines that printed on a paper tape were introduced around 1872. The samples pictured below were hand-driven but some later models replaced the cranks with electric motors. The number was entered on the keyboard and the crank on the right was pulled to print the number on the tape and add the number to the running total. When the user needed the running subtotal, the Subtotal key was held while the arm was cranked. The Total key was held to produce a final sum which also cleared the machine. (The Victors used a single sliding switch labeled S and T that was slid and held during the crank.) All of these models used the rocking segment mechanism.

## Burroughs Class 1/Model 9

This Burroughs Class 1 was one of the most spectacular adding machines made. It was quite imposing at 19" deep, over a foot tall and more than 63lbs. It had beveled glass walls on 3 sides allowing viewing of the rocking segment mechanism. (The segments and key stops are seen clearly in the front window.)

The printing mechanism was "blind" meaning the user couldn't see numbers as printed because they were behind the large machine. However, there was also a numeric register at the front of the machine just above the Burroughs logo. The printer had a wide carriage with a paper length setting and an end of page bell.

The red keys at the top allowed individual clearing of each column. The "C" key cleared the entire keyboard and the "R" key allowed repeated additions for multiplication. Total and Subtotal keys were also included.

These machines were made from 1905-1914 in models with 9, 11, and 17 digits - this 63 pounder is the smallest model. Options included fractions, dates, counting, and electric drive. There was also a similar class 2 series with two registers and a "transfer total" key to move numbers between the registers. Prices ranged from approximately \$300 to more than \$900 — Certainly not a trivial amount of money at the time.

The sample shown below was made in 1910. The 86-year old machine is still running smoothly and looking good.
Picture of the Class 1/Model 9 (~70K)
Side view showing the mechanism through the glass (~47K)
Close up on the numeric register seen through the front glass plate (~20K)

## Burroughs Portable

The picture below shows an early Burroughs "Portable" adding machine. (It certainly wouldn't be called portable today but compared to some of Burroughs' other models which weighed 90 pounds and had floor stands it was featherweight.)

It had an 8 column full keyboard plus keys for total, subtotal, non add, repeat (for multiplication) and Error (cleared the keyboard.) It also had a non print lever. This sample dates to the 1920's.
Picture of a Burroughs Portable adding machine (~41K)

## Dalton Ten Key

The Picture below shows an early ten key adding/printing machine, This model was introduced in 1902 and sold through 1928. It was the most successful and best known adding machine of its time. It was rugged, all metal and weighed 30 pounds but its upright design conserved desk space.

This model featured a "Multiplication" key which simply left the input number uncleared after addition so it could be added again. It also had non print, non add, correction (clear the entire input number) and backspace keys and a window indicated how many digits (but not the digits themselves) had been entered.
Picture of a Dalton ten key adding machine (~28K)

The picture below shows a Remington Rand adding machine. This very compact machine came in a black metal case. It had ten number keys plus total and clear keys. (The later on the front.) This machine was made around the 1930's.
Picture of a Remington Rand adding machine (~35K)

## Full Keyboard Victor

This was a later adding machine. It had a smaller, lighter bakelite body and a full keyboard. (Ten key and full keyboard adding machines coexisted for a long time.) The three position sliding switch to the left allowed subtraction and repeated addition and the sliding switch on the right produced totals and subtotals. Because of its full keyboard design, it didn't need a backspace key or an indicator of how many digits were entered.
Picture of Victor (~42K)

## Ten Key Victor

In addition to the "full keyboard" model shown above, a similar model was available in a ten key design which is shown below. A window above the keypad showed the number of digits entered (not the digits themselves) and the slide switch to the left was used to clear the current entry, or (if the user had a steady and precise hand) backspace incorrect digits.
Picture of a Victor "Ten Key" (~28K)

The later two machines above also had a switch for subtraction. This switch sprang back to the add position after each crank. The Dalton, like most earlier adding machines had complementary digits printed on each key for subtraction.

## Multiplication and Division on Adding Machines

While considered adding machines, all the models pictured in this section had some feature for making multiplication a reasonable chore. On the machines above, after entering one factor, a repeat/multiplication switch could be engaged. The machine could then be cranked as many times as the least significant digit in the other factor. Then the user reentered the first factor shifted left one position and continued on. Of course this was somewhat error-prone and the machine provided no direct indication of the two numbers multiplied.

Division was a greater chore. To divide, the user entered the dividend far enough to the left to produce the desired precision in the answer. The user then entered the divisor shifted as far to the left as possible so it could be subtracted without leaving a negative result. The user then held the combined repeat/subtract lever in the subtract position. (It had to be held in place since it would otherwise snap back and clear the divisor.) The user then cranked repeatedly to subtract the divisor as many times as possible. The painful part was that the machines didn't show the current subtotal. The user could either do the math mentally along with the machine to know when to shift the divisor, or could generate a subtotal by holding the subtotal switch while cranking. However, use of the subtotal switch required the poor user to return the subtract switch to the neutral (add) position and clear the keyboard. After generating the subtotal, the user needed to reenter the divisor (shifted appropriately) and return to holding the add/subtract/repeat switch in the subtract position. When the next subtraction would yield a negative result, the user shifted the divisor one place to the right and resumed subtracting.

Most four function mechanical models still performed repeated additions and subtractions but they didn't require any repeated entries of numbers, shifting numbers on the keyboard, or special operations to see the current subtotal during a divide.